I do use only red green and blue. And I can't take a screen shot because for some reason FeralHeart is not working for me. I'll just explain it as best I can.
The texture for the red, let's say DeepGreengrass, is placed down first. It covers the whole map including the places where the green and blue lay, which is not what I want.
Then the texture for the green, let's say ceiling, is placed and it too covers the whole map. Same goes for the blue texture. I have no idea where I went wrong.